(A) Male rat hearts were perfused (30 min) with Krebs Henseleit Buffer (KHB) alone or with 50 nM A61603, with/without 1 µM linsitinib. Samples were immunoblotted for phosphorylated (Phospho-) or total kinases. Representative blots are on the left with densitometric analysis on the right. (B and C) Neonatal rat cardiomyocytes were untreated (control), or exposed to 50 nM A61603 or 100 µM phenylephrine (PE) for 5 min with/without the indicated concentrations of linsitinib. Samples were immunoblotted for phospho- or total kinases. In B, representative blots are on the left with densitometric analysis on the right. Individual data points are shown with means ± SEM. In C, a representative experiment is shown. (D) Neonatal rat cardiomyocytes were untreated (control), or exposed to 50 nM A61603 (24 h) with/without 1 µM linsitinib. Cells were immunostained with antibodies to troponin T. Images from a representative experiment are on the left with assessment of cell area on the right. Individual data points are shown with the means ± SEM (n = 3–4 per group). Statistical analysis used one-way ANOVA with Holm–Sidak post-test.